U.S. patent number 6,962,751 [Application Number 10/167,751] was granted by the patent office on 2005-11-08 for amorphous carbon coated tools and method of producing the same.
This patent grant is currently assigned to Sumitomo Electric Industries, Ltd.. Invention is credited to Haruyo Fukui, Miki Irie, Satoru Kukino, Hideki Moriguchi, Kiyoshi Ogata, Hisanori Ohara, Satoshi Ohtani, Naoto Okazaki, Makoto Setoyama, Yoshiharu Utsumi.
United States Patent |
6,962,751 |
Fukui , et al. |
November 8, 2005 |
**Please see images for:
( Certificate of Correction ) ** |
Amorphous carbon coated tools and method of producing the same
Abstract
Amorphous carbon coated tools include substrates formed from a
cubic boron nitride sintered body, a diamond sintered body, a
silicon nitride sintered body, or an aluminum oxide-titanium
carbide sintered body, and amorphous carbon films thereon to make
the cutting edges of the tools. The amorphous carbon films contain
hydrogen at 5 atomic percent or below and have a maximum thickness
of 0.05 .mu.m to 0.5 .mu.m on the cutting edges. The amorphous
carbon films are most suitable for applications to cutting tools
exemplified by cutters, knives, and slitters, and to indexable
inserts used for example in turning tools including drills,
endmills, and reamers, and milling cutters.
Inventors: |
Fukui; Haruyo (Itami,
JP), Utsumi; Yoshiharu (Itami, JP), Irie;
Miki (Itami, JP), Ohara; Hisanori (Itami,
JP), Moriguchi; Hideki (Itami, JP), Kukino;
Satoru (Itami, JP), Setoyama; Makoto (Kyoto,
JP), Ohtani; Satoshi (Kyoto, JP), Okazaki;
Naoto (Kyoto, JP), Ogata; Kiyoshi (Kyoto,
JP) |
Assignee: |
Sumitomo Electric Industries,
Ltd. (Osaka, JP)
|
Family
ID: |
19019515 |
Appl.
No.: |
10/167,751 |
Filed: |
June 11, 2002 |
Foreign Application Priority Data
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|
|
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Jun 13, 2001 [JP] |
|
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2001-178887 |
|
Current U.S.
Class: |
428/408; 407/119;
428/156; 428/174; 428/212; 428/216; 428/325; 428/698; 51/307;
51/309 |
Current CPC
Class: |
C04B
41/009 (20130101); C04B 41/5001 (20130101); C04B
41/52 (20130101); C04B 41/85 (20130101); C04B
41/89 (20130101); C23C 14/0605 (20130101); C04B
41/5001 (20130101); C04B 41/4529 (20130101); C04B
41/52 (20130101); C04B 41/4529 (20130101); C04B
41/455 (20130101); C04B 41/5057 (20130101); C04B
41/52 (20130101); C04B 41/4529 (20130101); C04B
41/5133 (20130101); C04B 41/522 (20130101); C04B
41/52 (20130101); C04B 41/4529 (20130101); C04B
41/5001 (20130101); C04B 41/009 (20130101); C04B
35/117 (20130101); C04B 41/009 (20130101); C04B
35/584 (20130101); C04B 41/009 (20130101); C04B
35/581 (20130101); C04B 41/009 (20130101); C04B
35/52 (20130101); C04B 2111/00405 (20130101); Y10T
428/30 (20150115); Y10T 428/252 (20150115); Y10T
428/24942 (20150115); Y10T 407/27 (20150115); Y10T
428/265 (20150115); Y10T 428/24975 (20150115); Y10T
428/24628 (20150115); Y10T 428/24479 (20150115) |
Current International
Class: |
C04B
41/50 (20060101); C04B 41/45 (20060101); C04B
41/52 (20060101); C04B 41/85 (20060101); C04B
41/89 (20060101); C23C 14/06 (20060101); B23B
027/14 () |
Field of
Search: |
;428/408,698,336,216,472,469,325,174,156,212 ;407/119
;51/307,309 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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01252752 |
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07018415 |
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07-085465 |
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Mar 1995 |
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JP |
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07-192254 |
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Jul 1995 |
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JP |
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08119774 |
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May 1996 |
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JP |
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09-314405 |
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Dec 1997 |
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JP |
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10-025565 |
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Jan 1998 |
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JP |
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11-018809 |
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Jan 1999 |
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JP |
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11-086275 |
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Mar 1999 |
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JP |
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2000-176705 |
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Jun 2000 |
|
JP |
|
2001-062605 |
|
Mar 2001 |
|
JP |
|
Other References
Lifshitz "Hydrogen free amorphous carbon films: correlation between
growth conditions and properties" Diamond and Related Materials 5
(1996) 388-400. .
J.P. Hirvonen et al.; "Characterization and Unlubricated Sliding of
Ion-Beam-Deposited Hydrogen-Free Diamond-Like Carbon Films", Wear,
Lausanne, CH. vol. 141, 1990, pp. 45-58, XP000570574. .
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Cathodic Arc Evaporation", Thin Solid Films, Elsevier-Sequoia S. A.
Lausanne, CH., vol. 209, No. 2, Mar. 30, 1992; pp. 165-173
XP000362002, ISSN: 0040-6090. .
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Amorphous Diamond Coatings for Medical Applications", Diamond and
Related Materials, Elsevier Science Publishers, Amsterdam, NL, vol.
7, No. 2-5, Feb. 1, 1998, pp. 482-485, XP004115090, ISSN: 095-9635.
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and Mechanisms", Nuclear Instruments & Methods in Physics
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North-Holland Publishing Company, Amsterdam, NL, vol. 127-128, May
1, 1997, pp. 910-917, XP004096874, ISSN: 0168-583X. .
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Related Materials, Elsevier Science Publishers, Amsterdam, NL.,
vol. 8, No. 8-9, Aug. 1999, pp. 1659-1676, XP004254004, ISSN:
0925-9635. .
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Tetrahedral Amorphous Carbon", Diamond and Related Materials,
Elsevier Science Publishers, Amsterdam, NL., vol. 8, No. 7, Jul.
1999, pp. 1225-1228, XP004253920, ISSN: 0925-9635. .
R. Kalish et al., "Thermal Stability and Relaxation In
Diamond-Like-Carbon., A Raman Study of Films with Different SP3
Fractions (TA-C to A-C)", Applied Physics Letters, American
Institute of Physics, New York, US, vol. 74, No. 20, May 17, 1999,
pp. 2936-2938, XP000834705, ISSN: 0003-6951. .
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films grown by pulsed laser deposition", Europhysics Letters, May
15, 2000, Eur. Phys. Soc. by EDP Sciences and Soc. Italiana Fisica,
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0295-5075..
|
Primary Examiner: Turner; Archene
Attorney, Agent or Firm: Fasse; W. F. Fasse; W. G.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to U.S. application Ser. No.
10/167,770, filed Jun. 11, 2002.
Claims
What is claimed is:
1. An amorphous carbon coated tool comprising: a substrate
consisting of a body selected from the group consisting of a cubic
boron nitride sintered body, a diamond sintered body, a silicon
nitride sintered body, and an aluminum oxide-titanium carbide
sintered body; an interlayer disposed directly on said substrate,
wherein said interlayer comprises at least one carbide of at least
one element selected from the group consisting of Ti, Zr, Hf, V,
Nb, Ta, Cr, Mo, w, and Si, and wherein said interlayer has a
thickness in a range from 0.5 nm to less than 10 nm; and an
amorphous carbon film that: is disposed indirectly on said
substrate with said interlayer therebetween; covers at least a
cutting edge of said substrate; contains at most 5 atomic percent
of hydrogen; has a maximum thickness in a range from 0.05 .mu.m to
0.5 .mu.m on a tool edge of said substrate; has a density of up to
3.times.10.sup.5 particles/mm.sup.2 of macro particles comprising
carbon on a surface of said amorphous carbon film; has a peak in a
wave number region from 400 cm.sup.-1 to 1000 cm.sup.-1 in a Raman
spectrograph obtained by Raman spectroscopy using an argon ion
laser with a wavelength of 514.5 nm; is transparent in a visible
light range; and exhibits an interference color selected from the
group consisting of reddish purple, purple, bluish purple, blue,
Silver, yellow, red and green.
2. The amorphous carbon coated tool according to claim 1, wherein
said amorphous carbon film substantially consists solely of
carbon.
3. The amorphous carbon coated tool according to claim 1, wherein
said maximum thickness is no more than 0.25 .mu.m, and wherein said
tool edge on which said amorphous carbon film has said maximum
thickness is said cutting edge which is relevant to carrying out a
cutting process with said tool.
4. The amorphous carbon coated tool according to claim 1, wherein
said amorphous carbon film has a surface roughness Ra of 0.002
.mu.m to 0.05 .mu.m.
5. The amorphous carbon coated tool according to claim 1, wherein
said amorphous carbon film has a surface roughness Ry of 0.02 .mu.m
to 0.5 .mu.m.
6. The amorphous carbon coated tool according to claim 1, wherein
said amorphous carbon film has a Knoop hardness of 20 GPa to 50
GPa.
7. The amorphous carbon coated tool according to claim 1, wherein
said amorphous carbon film has a (I700/I1340) ratio of the
intensity of a peak present in the wave number region from 400
cm.sup.-1 to 1000 cm.sup.-1 (I700) relative to the intensity of
another peak found around 1340 cm.sup.-1 (I1340) in said Raman
spectrograph, said ratio being in the range from 0.02 to 2.5.
8. The amorphous carbon coated tool according to claim 1, wherein
said amorphous carbon film has a (S700/S1340) ratio of the integral
intensity of a peak present in the wave number region from 400
cm.sup.-1 to 1000 cm.sup.-1 (S700) relative to the integral
intensity of another peak present around 1340 cm.sup.-1 (S1340) in
said Raman spectrograph, said ratio being in the range from 0.01 to
2.5.
9. The amorphous carbon coated tool according to claim 1, wherein
said amorphous carbon film has a (I1340/I1560) ratio of the
intensity of a peak present around 1340 cm.sup.-1 (I1340) relative
to the intensity of another peak present around 1560 cm.sup.-1
(I1560) in said Raman spectrograph, said ratio being in the range
from 0.1 to 1.2.
10. The amorphous carbon coated tool according to claim 1, wherein
said amorphous carbon film has a (S1340/S1560) ratio of the
integral intensity of a peak present around 1340 cm.sup.-1 (S1340)
relative to the integral intensity of another peak present around
1560 cm.sup.-1 (S1560) in said Reman spectrograph, said ratio being
in the range from 0.3 to 3.
11. The amorphous carbon coated tool according to claim 1, wherein
said amorphous carbon film has a peak present at around 1560
cm.sup.-1 in the wave number range from 1560 cm.sup.-1 to 1580
cm.sup.-1 in said Raman spectrograph.
12. The amorphous carbon coated tool according to claim 1, further
comprising either a mixed composition layer having a mixed
component deriving from said interlayer and from said carbon film,
or a gradient composition layer having a gradually changing
composition, disposed between said interlayer and said amorphous
carbon film.
13. The amorphous carbon coated tool according to claim 1, adapted
to carry out processing of workpiece materials comprising at least
one of soft metals, nonferrous metals, organic materials, materials
containing hard particles, and printed circuit boards, or
bi-metallic cutting of a ferrous material and a soft metal.
14. The amorphous carbon coated tool according to claim 1, being a
tool selected from the group consisting of drills, micro drills,
endmills, an indexable insert for endmill processing, metal saws,
gear cutting tools, reamers, taps, and an indexable insert for
endmilling, milling cutting, and turning processing.
15. The amorphous carbon coated tool according to claim 1, wherein
said substrate consists of said cubic boron nitride sintered
body.
16. The amorphous carbon coated tool according to claim 1, wherein
said substrate consists of said diamond sintered body.
17. The amorphous carbon coated tool according to claim 1, wherein
said substrate consists of said silicon nitride sintered body.
18. The amorphous carbon coated tool according to claim 1, wherein
said substrate consists of said aluminum oxide-titanium carbide
sintered body.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to tools coated by amorphous carbon
films having wear resistance and an anti-adhesion feature, said
tools including cutting-off tools (represented by cutters, knives,
and slitters) and indexable inserts used for example in turning
tools and face milling cutter and milling cutters (exemplified by
drills, endmills, and reamers).
2. Description of the Background Art
Conventional cutting tools and wear-resistant tools have hard
coatings on the surface of substrates to enhance wear resistance
and the protection of the tool surface. The substrates consist of
such known materials as a WC-based sintered hard alloy, cermet, and
high-speed steel. It is also known that the hard coatings comprise
either a single layer or multiple layers of one or more of titanium
carbide, hafnium carbide, zirconium carbide, titanium nitride,
hafnium nitride, zirconium nitride, titanium carbonitride, hafnium
carbonitride, zirconium carbonitride, and aluminum oxide that are
produced through physical vapor deposition or chemical vapor
deposition.
In recent trends, however, cutting tools are used in operation at a
higher speed to improve processing efficiency, thus increasing the
temperature on the cutting edges thereof. Demands for specific
improvements in tool materials have also become stringent. It is
therefore essential to produce hard coatings that are more stable
at high temperatures, that is, more oxidation-resistant and more
adhered to the substrates. In addition, it has also become of
growing importance to enhance the wear resistance of the hard
coatings, namely hardness, for longer life of the cutting
tools.
Particularly in fields where high levels of hardness and strength
are required, a tool comprising a substrate formed from one of a
cubic boron nitride sintered body, a diamond sintered body, a
silicon nitride sintered body, or an aluminum oxide-titanium
carbide sintered body is used. A tool having said hard coating on
the surface of the substrate has been proposed.
For example, Japanese Patent Laying Open No. Tokukaihei No. 7-18415
proposes a cBN-based ceramic cutting tool covered by a single hard
layer or multiple hard layers having an average thickness of 5
.mu.m to 20 .mu.m. Said single hard layer is formed from one
selected from the group of TiC, TiN, TiCN, TiCO, TiCNO, and
Al.sub.2 O.sub.3, while said multiple hard layers consist of two or
more of the same group. Japanese Patent Laying Open No. Tokukaihei
No. 8-119774 also proposes a tool incorporating a substrate of
either a cBN sintered body or a diamond sintered body, and at least
one hard and thermal-resistant layer thereon to cover at least the
tool part relevant to the cutting process. Said layer contains at
least one element of C, N, and O, together with the primary
constituents of Ti and Al.
In recent years, workpiece materials to be cut have become diverse,
including such soft metals as aluminum alloys; nonferrous metals
including titanium, magnesium, and copper; organic materials;
materials containing hard particles like graphite; printed circuit
boards; and the combination of a ferrous material and aluminum for
bi-metallic cutting. Bi-metallic cutting is herein defined as the
simultaneous cutting process of a ferrous material adhered to
aluminum. In machining the workpiece materials herein listed, the
edge of a cutting tool is susceptible to such accumulation and
adhesion of said workpiece materials that increase cutting
resistance. In some cases, the cutting edge is chipped during the
process. These specific workpiece materials tend to cause far
greater wear of the cutting tool than do other workpiece
materials.
Diamond tools have conventionally been used in specific
applications including the processing of soft metals such as
aluminum and aluminum alloys, nonferrous metals represented by
titanium, magnesium, and copper, materials containing hard
particles like graphite, organic materials, printed circuit boards;
and the bimetallic cutting of a ferrous material adhered to
aluminum. Tools having diamond films formed on substrates tend to
have a rough surface due to the polycrystalline structures of the
films. It is necessary, therefore, to polish the tool surface for
applications in precision processing.
However, as a diamond film is the hardest among the existing
materials, there is no other alternative but to use diamond for
surface polishing, and this has made the cost higher.
TiN or other ceramic films obtained through physical vapor
deposition are usually as thick as 2 .mu.m to 3 .mu.m. On the other
hand, a diamond film needs to have a thickness of 20 .mu.m to 30
.mu.m initially. This is due to the fact that diamond crystals grow
at greatly varying speeds depending on their crystal orientation
and the formed film is subjected to polishing to obtain a smoother
surface. In addition, it is necessary to carry out etching and
remove graphite that also grows during the diamond film deposition.
This has decreased the film formation speed to one-tenth of the
speed that ceramic coats require, and made the production including
the coating process extremely expensive.
As with a tool wherein one of a diamond sintered body, a cBN
sintered body, a silicon nitride sintered body, or an aluminum
oxide-titanium carbide sintered body is brazed to a substrate,
there has existed the problem of providing a complicated shape and
a diameter as small as a few millimeters. When applied to a cutting
tool, those materials are insufficiently tough so as to cause the
cutting edge thereof to chip easily, abruptly ending the short
lifetime.
Thus the present invention mainly aims to provide amorphous carbon
coated tools for applications including the machining of soft
metals, nonferrous metals, organic materials, materials containing
hard particles, printed circuit boards, and the bimetallic cutting
of a ferrous material adhered to a soft metal. As the tool surface
has an excellent smooth feature, said tools effectively protect the
cutting edges from chipping and cause less corroded workpiece
materials to accumulate thereon. Furthermore, a high thermal
conductivity of said tools curbs a temperature increase on said
cutting edges and enables applications under severe conditions such
as dry cutting and high-speed machining. Another object of the
present invention is to provide the method of producing said
tools.
SUMMARY OF THE INVENTION
The aforementioned objects of the present invention can be attained
by specifying the composition of said substrates and the thickness
of amorphous carbon films thereon.
An amorphous carbon coated tool recited in the present invention
comprises a substrate of one selected from the group of a cBN
sintered body, a diamond sintered body, a silicon nitride sintered
body, and an aluminum oxide-titanium carbide sintered body; and an
amorphous carbon film covering at least the cutting edge thereof
Said amorphous carbon film is characterized by hydrogen contained
at 5 atomic percent or below and a maximum thickness of 0.05 .mu.m
or more to 0.5 .mu.m or less on the cutting edge.
Another amorphous carbon coated tool herein provided comprises a
substrate of one selected from the group of a cBN sintered body, a
diamond sintered body, a silicon nitride sintered body, and an
aluminum oxide-titanium carbide sintered body; and an amorphous
carbon film covering at least the cutting edge thereof. Said
amorphous carbon film is characterized in that graphite is used as
a raw material and formed into a film through physical vapor
deposition in an atmosphere substantially reducing hydrogen, and
the formed film has a maximum thickness of 0.05 .mu.m or more to
0.5 .mu.m or less on the cutting edge.
The amorphous carbon coated tool production method according to the
present invention comprises a step of holding a substrate of one
selected from the group of a cBN sintered body, a diamond sintered
body, a silicon nitride sintered body, and an aluminum
oxide-titanium carbide sintered body in a vacuum chamber; and
another step of applying a zero or negative DC bias voltage to said
substrate while evaporating graphite and enabling the formation of
an amorphous carbon film. Said method is also characterized by
limiting the maximum thickness of said amorphous carbon film to a
range from 0.05 .mu.m to 0.5 .mu.m on the cutting edge of said
tool.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic view of a vacuum chamber used in the film
formation process according to the present invention.
FIG. 2 is a cross section view of a cutting edge of a tool produced
according to the present invention.
FIG. 3 is a Raman spectrum of an amorphous carbon film manufactured
according to the present invention.
FIG. 4 is a Raman spectrum of an amorphous carbon film produced by
a conventional method.
DETAILED DESCRIPTION OF THE INVENTION
The following are details of preferred embodiments and compositions
in implementing the present invention.
A Substrate Comprising a Sintered Body
A Substrate of a Diamond Sintered Body
It is preferable that the diamond sintered body contain diamond at
40 volume percent or over. More preferably, the diamond sintered
body has such a composition as follows.
(1) The diamond sintered body contains diamond from 50 volume
percent to 98 volume percent and the remaining part consisting of a
ferrous metal, WC, and inevitable impurities. It is particularly
desirable that said ferrous metal is Co.
(2) The diamond sintered body contains diamond from 85 volume
percent to 99 volume percent and the remaining part formed of
pores, WC, and inevitable impurities.
(3) The diamond sintered body contains diamond from 60 volume
percent to 95 volume percent and the remaining part consisting of
WC; inevitable impurities; and at least one selected from the group
of ferrous metals and the carbides and carbonitrides of elements
belonging to the IVa, Va, and VIa groups in the periodic table. It
is further preferable that the remaining part comprise a binder of
Co, TiC, WC, and inevitable impurities.
(4) The diamond sintered body contains diamond from 60 volume
percent to 98 volume percent, and the remaining part formed of
tungsten carbide, inevitable impurities, and either silicon or
silicon carbide.
A Substrate of a cBN Sintered Body
It is preferable that the cBN sintered body contain cBN at 30
volume percent or over. More preferably, the cBN sintered body has
a composition described below.
(1) The cBN sintered body contains cBN from 30 volume percent or
more to 80 volume percent or less and the remaining part formed
from at least one selected from the group of the nitride, boride,
carbide, and solid solution of an element belonging to the IVa, Va,
and VIa groups in the periodic table; a binder comprising an
aluminum compound; a ferrous metal and inevitable impurities.
In the cBN sintered body having said composition, cBN particles are
bonded mainly by said binder having low affinity with iron. The
bond is sufficiently strong so as to improve the wear resistance
and the strength of the tool wherein said substrate is
incorporated.
Said cBN sintered body must have cBN from 30 volume percent or more
to 80 volume percent or less. When the percentage is lower than 30
volume percent, the cBN sintered body is not hard enough to cut
hardened steel and other workpiece materials having a high
hardness. The percentage of over 80 volume percent makes it
difficult for a binder to bond cBN particles together and reduces
the strength of the cBN sintered body.
(2) The cBN sintered body contains cBN from 80 volume percent or
more to 90 volume percent or less, has cBN particles bonded, and
also contains the remaining part formed from inevitable impurities
and a binder mainly consisting of either an Al compound or a Co
compound. In said cBN sintered body, either an Al or Co-contained
metal that can act as a catalyst, or an intermetallic compound is
used as a raw material and subjected to liquid-phase sintering to
bond cBN particles together. Said liquid-phase sintering process
makes it possible to increase the cBN particles contained in said
cBN sintered body. With a high percentage of cBN particles, the cBN
sintered body becomes less wear-resistant. On the other hand, the
cBN particles have a strong skeleton structure that effectively
protects the cutting edge of a tool from chipping and permits
applications of the tool in the cutting processing under severe
conditions.
Said cBN sintered body contains cBN from 80 volume percent or more
to 90 volume percent or less. When the percentage is below 80
volume percent, it is difficult for cBN particles therein to bond
together and form a skeleton structure. If the percentage exceeds
90 volume percent, the quantity of said binder comprising either
said catalytic Al or Co-contained metal or said intermetallic
compound is insufficient so as to leave a part of said body
unsintered, thereby lowering the strength of the tool.
A Substrate of a Silicon Nitride Sintered Body
It is preferable that the silicon nitride sintered body contain
silicon nitride at 90 volume percent. More preferably, said silicon
nitride sintered body contain silicon nitride produced through hot
isostatic pressing (HIP) of 90 volume percent or over. It is
desirable that the remaining part of said silicon nitride sintered
body be formed from inevitable impurities and a binder consisting
of at least one selected from the group of aluminum oxide, aluminum
nitride, yttrium oxide, magnesium oxide, zirconium oxide, hafnium
oxide, rare earths, TiN, and TiC. The silicon nitride in said
sintered body is set at 90 volume percent. If the silicon nitride
is below 90 volume percent, the silicon nitride sintered body lacks
in hardness
A Substrate of an Aluminum Oxide-titanium Carbide Sintered Body
It is preferable that the aluminum oxide-titanium carbide sintered
body contain aluminum oxide from 20 volume percent to 80 volume
percent and titanium carbide from 15 volume percent to 75 volume
percent. Also preferably, the remaining part of said sintered body
comprises inevitable impurities and a binder formed of one oxide of
Mg, Y, Ca, Zr, Ni, Ti, or TiN. The aluminum oxide in said sintered
body should be limited to the range of 20 volume percent to 80
volume percent. When the percentage is below 20 volume percent, it
is difficult to achieve a predetermined density. With the
percentage exceeding 80 volume percent, said body lacks in hardness
and becomes less wear-resistant. The titanium carbide in said
sintered body must be from 15 volume percent to 75 volume percent.
If the percentage is below 15 volume percent, said sintered body
has insufficient hardness and is less wear-resistant. With the
percentage exceeding 75 volume percent, it is difficult to achieve
a predetermined density.
An Amorphous Carbon Film
Amorphous carbon films include those generally called hard carbon
films, diamond-like carbon (DLC) films, a-C:H films, and i-C films.
On the other hand, an amorphous carbon film produced according to
the present invention has the characteristics described below.
Film Deposition Methods
In the present invention, graphite is used as a raw material and
formed into an amorphous carbon film through physical vapor
deposition in an atmosphere substantially not containing hydrogen.
The film has a high hardness equivalent to that of diamond and
exhibits excellent wear-resistance features when incorporated in
cutting tools. An amorphous carbon film employing hydrocarbon as a
raw material contains hydrogen, which differentiates the film from
those provided by the present invention.
The amorphous carbon film of the present invention is formed solely
of carbon atoms except the inevitable impurities emerging during
the film deposition process. This allows the film to achieve a
higher ratio of sp.sup.3 bonding than the hydrogen-contained
amorphous carbon film, making it possible to improve hardness. At
the same time, the oxidation resistant feature of the film can also
be improved to nearly the same level as diamond, which begins
oxidation at around 600.degree. C. Though having been produced in
an atmosphere substantially not containing hydrogen, the film may
find hydrogen contained at about 5 atomic percent or below. It is
conceivable that depending on the vacuum level during the film
deposition process, hydrogen or water remaining inside the vacuum
chamber may be absorbed in the amorphous carbon film.
Among the physical vapor deposition methods using graphite as a raw
material, those usually employed in industries such as cathode arc
ion plating, laser ablation, and sputtering deposition are very
effective in forming amorphous carbon films at a high speed and
solving the problem of high costs arising from diamond film
production. Cathode arc ion plating is particularly desired for
such film deposition in terms of the adhesiveness and hardness of
the obtained film. By ionizing the raw material at a high level,
the cathode arc ion plating method allows carbon ions to be
irradiated on substrates to form an amorphous carbon film thereon.
As a result, the ratio of sp.sub.3 bonded carbons in said film is
sufficiently high to make the film compact and very hard, thus
lengthening the lifetime of the tool.
The temperature of the substrate is preferably in the range of
50.degree. C. to 200.degree. C. When the temperature is over
350.degree. C., graghite is liable to deposit on the substrate
instead of amorphous carbon. The temperature of the substrate
increases during deposition of the amorphous carbon, because a
carbon ion irradiates the substrate. The temperature of the
substrate therefore may become practically in the suitable range
for deposition without heating by a heater. On the other hand, the
temperature of the substrate may be controlled by heating or
cooling.
The temperature of the substrate is more preferably in the range of
50.degree. C. to 150.degree. C.
Macro Particle Density
On the surface of an amorphous carbon film produced through the
cathode arc ion plating method, there exist hard particles called
macro particles. A lower macro particle density is desirable, as it
causes less resistance to the cutting process. The density should
be up to 3.times.10.sup.5 particles/mm.sup.2, and more preferably,
no more than 1.5.times.10.sup.5 particles/mm.sup.2. Needless to say
that the ultimately desired density should be 0 particle/mm.sup.2.
If the density exceeds 3.times.10.sup.5 particles/mm.sup.2,
workpiece materials tend to corrode and adhere to the macro
particles, thereby increasing the cutting resistance.
The macro particle density on the amorphous carbon film can be
evaluated by means of scanning electron microscope (SEM)
observation. The SEM observation should be conducted after a
precious metal like Pt or Pd is vapor deposited on the surface of a
sample film through ion sputtering or other methods. A photograph
should be taken of the sample film surface at a magnification of
1000 times or over. By counting the number of macro particles
observed in the photograph, the macro particle density can be
determined.
FIG. 2 is a cross sectional view of an amorphous carbon film 20 to
show the growth of macro particles 21 thereon. The amorphous carbon
film 20 is in the process of being deposited on a cutting edge 23
of a tool. During this process, graphite particles 22 are flying
and falling on the film surface. The graphite particles 22 cause
protrusions to appear on the film surface. By electron microscope
examination, round grains 21 in different diameters are confirmed
present on the film surface. However, the presence of the round
grains 21 is undesirable according to the present invention. Since
the graphite particles 22 tend to fly during the film formation
process, the graphite particles 22 assumably exist in various
depths of the amorphous carbon film 20 as illustrated in FIG.
2.
It is recommendable that such means as low-energy film deposition
and magnetic field filtration are used to improve the surface
smoothness of the amorphous carbon film, as they can prevent said
round particles from flying out of the raw material of
graphite.
Surface Roughness
The surface roughness of the amorphous carbon film is desirably in
a range of 0.002 .mu.m or more to 0.05 .mu.m or less according to
the Ra definition specified under the JIS standard B0601.
Considering applications to a cutting tool, the film should have
the smallest possible surface roughness (an Ra value). In
actuality, however, the Ra value can never be lowered to zero. As a
result of various cutting tests, it was discovered that when the Ra
value was 0.05 .mu.m or below, less workpiece material corroded and
accumulated on the cutting edge and the cutting operation
performance improved. It is also desirable that the surface
roughness of the amorphous carbon film be in a range from 0.02
.mu.m or more to 0.5 .mu.m or less according to the Ry definition
specified under the JIS standard B0601. With the Ry value exceeding
0.5 .mu.m, protrusions (macro particles) on the surface of the
amorphous carbon film may allow corroded workpiece material to
accumulate thereon, leading to increased cutting resistance.
Thickness
An amorphous carbon film must be as thick as 0.05 .mu.m to 0.5
.mu.m at maximum on the cutting edge of a tool. If the thickness is
below 0.05 .mu.m, a problem arises in the wear resistance of the
tool. With the thickness exceeding 0.5 .mu.m, internal stress
accumulated within the amorphous carbon film grows to the extent
that it may cause the film to peel and chip. Specifying the film
thickness as 0.5 .mu.m or below allows small macro particles to
exist less densely on the film surface. This is also effective in
limiting the surface roughness to 0.05 .mu.m or below (according to
the aforementioned Ra definition), or to 0.5 .mu.m or below
(according to the aforementioned Ry definition). As indicated with
a T in FIG. 2, the amorphous carbon film is thicker on the tip of
the cutting edge. If the film is thinner on the tip, the machining
performance of the tool improves. In light of anti-adhesion, it is
preferred that the amorphous carbon film on the tool edge relevant
to the cutting process have a maximum thickness of 0.05 .mu.m or
more to 0.25 .mu.m or less.
Hardness
It is desirable that an amorphous carbon film have a Knoop hardness
in a range from 20 GPa or more to 50 GPa or less. If the hardness
is below 20 GPa, the amorphous carbon film may have insufficient
wear resistance. With a hardness exceeding 50 GPa, the
anti-chipping feature of the tool edge may deteriorate. More
preferably, the amorphous carbon film has a Knoop hardness of 25
GPa or more to 40 GPa or less.
Raman Spectrum
It is extremely difficult to define the structure of an amorphous
carbon film, due to its intrinsic quality. As a result of the
evaluation of various amorphous carbon films, it was discovered
that Raman spectrum showed differences in film structures.
While FIG. 3 shows a Raman spectrum of an amorphous carbon film
produced according to the present invention, FIG. 4 is a Raman
spectrum of a conventional hydrogen-contained amorphous carbon
film. Both spectra were obtained through the Raman spectrum
analysis employing an argon gas laser with a wavelength of 514.5
nm. The result of the measurement is shown by a solid line in FIG.
4, which has a peak at around 1340 cm.sup.-1 as opposed to around
700 cm.sup.-1.
Secondly, background signals were subtracted from the obtained
spectra to break down said spectra into two partial spectra
respectively. On the assumption that the two spectra having peaks
indicate values to which two Gauss functions have been applied, the
values were approximated by means of a non-linear least square
regression to separate them into two peaks respectively. The
obtained results are shown in chain lines. The heights of
pronounced peaks found around 1340 cm.sup.-1 and 1560 cm.sup.-1 are
indicated respectively as I1340 and I1560. In contrast, as shown by
the solid line in FIG. 3, it was difficult to identify the presence
of a peak at around 1340 cm.sup.-1 in the original Raman spectrum
of the film produced according to the present invention. Instead, a
broad and slight rise was confirmed present at around 700
cm.sup.-1. The spectrum was also broken down into two partial
spectra in the aforementioned method, and the result is indicated
by chain lines in FIG. 3. In a comparison between FIGS. 3 and 4, it
is apparent that the peak at around 1340 cm.sup.-1 in FIG. 3 is not
as high or sharp as the peak appearing in the same wave number
region in FIG. 4. The intensity of the peak at around 700 cm.sup.-1
is indicated as 1700. The individual peaks were calculated into
integral values as referenced for example by S700.
In the amorphous carbon film produced according to the present
invention, peaks were observed in three wave number regions: from
400 cm.sup.-1 or more to 1000 cm.sup.- or less, around 1340
cm.sup.-1, and around 1560 cm.sup.-1. With a conventional
hydrogen-contained film, however, no peak was detected in lower
wave numbers from 400 cm.sup.-1 or more to 1000 cm.sup.-1 or less.
A structure having a peak in the wave number region from 400
cm.sup.-1 to 1000 cm.sup.-1 enables the film to improve hardness
and wear resistance.
Furthermore, the wear resistance of the tool improves, if the ratio
(I700/I1340) of the peak intensity located in the wave number range
from 400 cm.sup.-1 or more to 1,000 cm.sup.-1 or less (I700) and
the peak intensity occurring around 1340 cm.sup.-1 (I1340) is in a
range from 0.01 or more to 2.5 or less. It can be assessed that an
increase in the amount of either tiny graphite or sp.sup.3 bonded
carbons having strain allowed the amorphous carbon film to achieve
a high level of hardness.
Aside from the aforementioned evaluation method using a peak
intensity, an assessment can be made by means of an integral
intensity ratio of the obtained peaks. Preferably, the ratio
(S700/S1340) of the integral intensity located in the wave number
region from 400 cm.sup.-1 to 1,000 cm.sup.-1 (S700) and the
integral intensity found around 1340cm.sup.-1 (S1340) should be in
a range of 0.01 to 2.5. If said ratio is below 0.01, the amorphous
carbon film has the same level of wear resistance as the
conventional film. Although a variety of film deposition tests were
conducted as described hereinafter, an amorphous film having the
integral intensity ratio of 2.5 or over was not obtained.
An amorphous carbon favorably exhibits a high level of wear
resistance, when the ratio (I1340/I1560) of the peak intensities
occurring around 1560 cm.sup.-1 (I1560) and around 1340 cm.sup.-1
(S1340) is in a range from 0.1 or more to 1.2 or less. The
I1340/I1560 ratio is also interpreted as an sp.sup.2 /sp.sup.3
ratio and indicates the amount of bonded carbons present inside the
amorphous carbon film. Although the ratio does not directly
indicate the amount of sp.sup.2 bonded carbons in the film, it
provides an instrument for relative structure evaluation. It was
found that if there was a pronounced peak around 1560 cm.sup.-1,
the film became harder. With a strong sp.sup.3 bond, the wear
resistance of the film improved. Aside from the peak intensity, the
ratio (S1340/S1560) of the peak integral intensities occurring
around 1560 cm.sup.-1 (S1560) and around 1340 cm.sup.-1 (S1340)
should be in a range from 0.3 or more to 3 or less.
When the peak occurring around 1560 cm.sup.-1 exists in the wave
number region from 1560 cm.sup.-1 or more to 1580 cm.sup.-1 or
less, a high level of wear resistance can be achieved. The location
of a peak in a Raman spectrum varies depending on the stress state
inside the film. In general, if compression is strong, the peak
shows a shift to a high wave number region. In contrast, when
tension is strong, the peak location is shifted to a lower wave
number region. It was found that where there was strong compression
in the film, the wear resistance of the film improved.
Interference Color
Amorphous carbon films employed for the prior art are not
transparent in the visible light range, and have a dark brown or
black color. In contrast, the amorphous carbon film produced
according to the present invention is characterized by its
transparency in the visible light range and its interference
color.
An amorphous carbon film having an interference color denotes the
abundance of sp.sub.3 bonded carbons therein. At the same time, it
shows that the film has the physical features of a refractive
index, optical band gap, and elasticity more similar to diamond
than to conventional amorphous carbon films. When applied in tools,
the film produced according to the present invention exhibits a
high level of resistance to wear and heat due to a high level of
hardness. Thus, tools wherein the present invention is optimized
have a noticeable characteristic of interference colors.
According to an increase in the thickness of the amorphous carbon
film, its color also changes from (1) brown, (2) reddish purple,
(3) purple, (4) bluish purple, (5) blue, (6) silver, (7) yellow,
(8) red, (9) blue, (10) green, (11) yellow, to (12) red. After
reaching (12) red, the color again changes into (8) red, and
continues to change in the same manner until it becomes (12) red.
These color changes are sequential relative to the film thickness.
When said thickness is between two of the aforementioned color
indices, the film shows an intermediate or transitional color.
Assessments made by inventors resulted in a finding that if the
maximum thickness of the film on the cutting edge is specified as a
range from 0.05 .mu.m to 0.5 .mu.m, the film should be in a color
from (2) reddish purple to (10) green. The color should not
necessarily be pure; iridescent colors are acceptable. Furthermore,
it is also effective to cover an amorphous carbon film with a
conventional amorphous film in dark brown or black.
Interlayer
It is preferable that a tool produced according the present
invention have an interlayer between a substrate and an amorphous
carbon film thereon to allow a stronger adherence of the film to
the substrate.
Material
It is preferable that said interlayer is formed from at least one
element selected from the group consisting of an element from
groups IVa, Va, VIa, III b of the periodic table and an element
from group IVb of the periodic table except C, or at least one
carbide of an element selected from the aforementioned groups.
More preferably, the interlayer is formed from at least one element
selected from the group consisting of elements Ti, Zr, Hf, V, Nb,
Ta, Cr, Mo, W, and Si, or at least one carbide of an element
selected from the aforementioned group. As these metal elements can
easily create a strong bond with carbon, having an amorphous carbon
film on the interlayer comprising either an aforementioned metal
element or an aforementioned metal carbide allows a stronger
adherence of the film to the substrate.
Thickness
The thickness of the interlayer should be 0.5 nm or over, but no
more than 10 nm. Being thinner than the minimum limit, the
interlayer does not function as anticipated. When the thickness
exceeds the maximum limit, the adhesiveness of the film is at the
same level as films provided by the prior art. Inserting such an
extremely thin interlayer makes it possible to achieve the stronger
adhesion between the film and the substrate than the prior art
could offer. This may also lead to a remarkable improvement of the
lifetime of the tools.
Mixed Composition Layer and Gradient Composition Layer
It is further desirable that either a mixed composition layer or a
gradient composition layer is inserted between the amorphous carbon
film and the interlayer to achieve far stronger adhesion. While a
mixed composition layer forms a mixture of the composition of each
film, a gradient composition layer has a sequentially changing
composition therein. These two layers cannot be clearly
distinguished. When the production conditions are altered from the
formation of an interlayer to the deposition of an amorphous carbon
film, these different compositions usually mix and form either a
mixed composition layer or a gradient composition layer. Difficult
as it is to confirm directly the presence of such layers, it can be
construed from the results of examination using X-ray
Photo-electronic Spectroscopy (XPS) and Auger Electron Spectroscopy
(AES).
Applications of Tools
The amorphous carbon coated tools of the present invention are
appropriate for the processing of aluminum and aluminum alloys, as
the tools have excellent wear-resistant and anti-adhesion features.
The tools are most appropriate for the machining of such nonferrous
metals as titanium, magnesium, and copper. The tools can also be
used for the cutting of materials containing hard particles such as
graphite and organic and other materials, the machining of printed
circuit boards, and the bimetallic cutting of a ferrous material
adhered to aluminum. Furthermore, due to their high hardness, the
amorphous carbon films can be optimized in tools for the processing
not only of nonferrous materials, but also of stainless and other
steel and castings.
Specific Example of Tools
The amorphous carbon coated tools recited in the present invention
may find particular utility in applications involving tools
selected from the group of drills, endmills, metal saws, gear
cutting tools, reamers, taps, and indexable inserts used in the
endmilling, milling cutting, and turning processing.
As described heretofore, coated tools produced according to the
present invention can maintain wear resistance and improve their
anti-adhesion feature, as said tools employ substrates of specific
compositions and amorphous carbon films having a specific
thickness. Furthermore, it is also possible to extend the cutting
length and the lifetime of said tools. Manufacturing an amorphous
carbon film containing little hydrogen makes it possible to further
improve the resistance to wear and adhesion of the tools. In light
of this, it is anticipated that the present invention may find
particular utility in applications to an indexable insert used for
example in turning tools and face milling cutter and milling
cutters (including drills, endmills, and reamers), as well as for
cutting tools (represented by cutters, knives, and slitters).
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Amorphous carbon coated tools produced according to the present
invention are described in detail by using Example Embodiments.
However, conceivable embodiments are not limited to those herein
provided, and any other means employing physical vapor deposition
of graphite is deemed effective.
EXAMPLE 1
Cemented carbide drills with an 8 mm diameter wherein substrates of
sintered bodies were brazed on the cutting edges were prepared. The
following is a description of the sintered bodies (Types A to H)
employed as the substrates in the Example Embodiments.
Types of sintered bodies A: A sintered body containing diamond
particles with a particle size from 0.1 .mu.m or more to 2 .mu.m or
less at 93 volume percent, and the remaining part comprising Co,
WC, and inevitable impurities. B. A sintered body containing
diamond particles with a particle size from 0.1 .mu.m or more to 2
.mu.m or less at 80 volume percent, and the remaining part
comprising pores, WC, and inevitable impurities. C. A sintered body
containing diamond particles with a particle size from 0.1 .mu.m or
more to 2 .mu.m or less at 90 volume percent, and the remaining
part comprising Co, TiC, WC, and inevitable impurities. D. A
sintered body containing diamond particles with a particle size
from 0.1 .mu.m or more to 2 .mu.m or less at 98 volume percent, and
the remaining part comprising SiC, WC, and inevitable impurities.
E. A sintered body containing cBN particles with a particle size
from 0.1 .mu.m or more to 5 .mu.m or less at 70 volume percent, and
the remaining part being Co, inevitable impurities, and a binder
formed from TiN, TiB.sub.2, AlN, AlB.sub.2, WC, and Al.sub.2
O.sub.3. F. A sintered body containing cBN particles with a
particle size from 0.1 .mu.m or more to 5 .mu.m or less at 80
volume percent, and the remaining part being inevitable impurities
and a binder formed from AlN, AlB.sub.2, and Al.sub.2 O.sub.3. G. A
sintered body containing silicon nitride particles with an average
size of 1.5 .mu.m at 95 volume percent, and the remaining part
being a binder formed from Al.sub.2 O.sub.3, AlN, MgO, TiN, and
TiC, and inevitable impurities. H. A sintered body containing
aluminum oxide particles with an average size of 1.5 .mu.m in at 67
volume percent and titanium nitride particles with an average size
of 1.5 .mu.m at 28 volume percent, and the remaining part being a
binder of MgO and CaO, and inevitable impurities.
A known method of cathode arc ion plating was conducted for the
surface of said substrates to prepare amorphous carbon coated
drills (Samples 1 to 21) according to the present invention as
shown in Table 1.
As indicated in FIG. 1, a plurality of targets 2 and 3 were placed
inside a vacuum chamber 1. Cemented carbide drills 5 wherein the
aforementioned sintered bodies were brazed on the cutting edges
were installed on a substrate holder 4. The substrate holder was
rotatable in the middle of said targets 2 and 3. Power sources 7
and 8 were adjusted to change ion arc electric discharge. The
amount of evaporated target material was controlled while amorphous
carbon formed films on the drills.
First, substrate heaters 6 were used to increase the temperature to
100.degree. C. while the vacuum level inside the vacuum chamber 1
was adjusted to 2.times.10.sup.-3 Pa. Argon gas was then supplied
to the vacuum chamber 1, while the atmosphere therein was held at
the vacuum level of 2.times.10.sup.-1 Pa. At the same time, argon
plasma cleaning was carried out on the substrate holder 4 by
applying -1000 volts from a bias power source 9 before the
discharge of argon gas. Gas was supplied through a gas inlet 10,
and discharged through an exhaust port 11.
Secondly, prior to the deposition of amorphous carbon films,
targets of a metal element belonging to the IVa, Va, VIa, and IIIb
groups in the periodic table were evaporated and ionized. At the
same time, -1000 volts were applied to the substrate holder 4 from
the bias power source 9 to carry out metal ion bombardment. Etching
was also conducted for the surface of the films for further
strengthened adherence.
With or without the introduction of hydrocarbon gas, the targets
comprising one element selected from the group consisting of an
element from groups IVa, Va, VIa, IIIb of the periodic table and an
element from group IVb except C in the periodic table were
evaporated and ionized. Voltages of a few hundred negative volts
were applied from the bias power source 9 to the substrate holder 4
to cause either the metals or the metal carbides to form
interlayers. The interlayer and amorphous carbon films were formed
as a result of changing the targets and the atmosphere. Such
changes usually cause two layers to mix compositions, albeit
slightly. It can be deduced, therefore, that there exists a mixed
composition layer or a gradient composition layer between the two
layers.
Evaporating and ionizing the targets of graphite through cathode
arc electric discharge permitted amorphous carbon films to form on,
and in contact with, cemented carbide drills. The voltages applied
from the bias power source 9 were set as a few hundred negative
volts. The temperature of the cemented carbide drills was
100.degree. C.
For comparison, coated drills (Comparative Examples 1 to 8) were
prepared as shown in FIG. 1. Sintered bodies employed in the
Comparative Examples were of Type A. Comparative Example 1 was the
same cemented carbide drill as provided heretofore, and had a
hydrogenated amorphous carbon film formed thereon by the use of a
conventional plasma CVD film deposition apparatus that employed
CH.sub.4 gas as a raw material. Comparative Examples 2 to 4 were
the same cemented carbide drills as provided heretofore, and each
said drill had an amorphous carbon film formed thereon through the
cathode arc ion plating method employing graphite as a raw
material. However, the films in Comparative Examples 2 to 4 did not
have a thickness in the range herein specified. Comparative Example
5 was the same cemented carbide drill as provided heretofore, and
had a hydrogenated amorphous carbon film formed thereon through the
cathode arc ion plating method wherein CH.sub.4 gas was added to
the atmosphere. However, the amount of hydrogen contained in the
film was out of the range herein specified. Comparative Examples 6
and 7 were the same cemented carbide drills as provided heretofore,
and had coatings respectively formed from TiN and TiAlN through the
cathode arc ion plating method. Comparative Example 8 was a drill
having no film thereon.
Then, a drilling test was conducted under the conditions specified
in Table III (wet conditions with oil supply from outside) for each
of the drills produced in the aforementioned methods. Concerning
each said drill, a reduction ratio of thrust resistance was
measured in comparison with Comparative Example 8 as a standard.
Examination was also made concerning the presence of corroded
workpiece material adhered to the cutting edge thereof. The results
of the drilling test are disclosed in Table II. The amount of
hydrogen in the obtained amorphous carbon film was evaluated
through the Elastic Recoil Detection Analysis (ERDA). The thickness
of each said film on the cutting edge was measured by conducting
SEM observation of the cross section of the cutting edge.
TABLE I Amount of Maximum hydrogen thickness Color of Macro Film
contained of film on film on Surface Surface particle Knoop
deposition in film cutting cutting Type of roughness roughness
density hardness Component of method (atomic %) edge (.mu.m) edge
substrate Ra (.mu.m) Ry (.mu.m) (count/mm.sup.2) (GPa) interlayer
Sample 1 Cathode arc 3.5 0.05 Reddish A 0.002 0.02 23000 23 Ti ion
plating purple Sample 2 Cathode arc 4.9 0.07 Purple B 0.003 0.05
35000 24 TiCx ion plating Sample 3 Cathode arc 2.2 0.08 Bluish C
0.004 0.06 41000 21 Zr ion plating purple Sample 4 Cathode arc 1.3
0.10 Blue D 0.005 0.08 52000 22 ZrCx ion plating Sample 5 Cathode
arc 1.1 0.12 Silver E 0.006 0.09 57000 35 Cr ion plating Sample 6
Cathode arc 0.7 0.15 Yellow F 0.008 0.11 72000 31 CrCx ion plating
Sample 7 Cathode arc 1.4 0.20 Red G 0.009 0.12 110000 34 V ion
plating Sample 8 Cathode arc 0.4 0.25 Blue H 0.015 0.19 125000 36
VCx ion plating Sample 9 Cathode arc 0.1 0.30 Green A 0.021 0.23
153000 39 Nb ion plating Sample 10 Cathode arc 0.3 0.35 Yellow B
0.026 0.32 172000 40 NbCx ion plating Sample 11 Cathode arc Not
0.40 Red A 0.029 0.35 212000 42 Ta ion plating detectable Sample 12
Cathode arc Not 0.45 Blue B 0.035 0.39 251000 43 TaCx ion plating
detectable Sample 13 Cathode arc Not 0.50 Green F 0.045 0.41 259000
46 Hf ion plating detectable Sample 14 Cathode arc Not 0.05 Reddish
F 0.003 0.02 24000 48 HfCx ion plating detectable purple Sample 15
Cathode arc Not 0.07 Purple G 0.003 0.04 31000 47 Mo ion plating
detectable Sample 16 Cathode arc Not 0.08 Bluish H 0.004 0.06 39000
47 MoCx ion plating detectable purple Sample 17 Cathode arc 1.4
0.10 Blue A 0.006 0.08 49000 23 W ion plating Sample 18 Cathode arc
2.3 0.12 Silver B 0.007 0.09 62000 23 WCx ion plating Sample 19
Cathode arc 3.5 0.15 Yellow C 0.009 0.11 71000 25 Si ion plating
Sample 20 Cathode arc 1.9 0.20 Red D 0.015 0.17 120000 26 SiCx ion
plating Sample 21 Cathode arc 2.2 0.15 Yellow F 0.009 0.10 73000 30
N.A. ion plating Comparative Plasma 40 0.30 Dark A 0.003 0.04 0 12
Si Example 1 CVD brown Comparative Cathode arc 1.6 0.03 Brown A
0.002 0.03 21000 31 TiCx Example 2 ion plating Comparative Cathode
arc 0.4 0.60 Red F 0.061 0.63 330000 34 VCx Example 3 ion plating
Comparative Cathode arc 2.2 1.00 Gray G 0.082 0.83 395000 32 ZrCx
Example 4 ion plating Comparative Cathode arc 32 0.15 Gray A 0.007
0.07 76000 14 CrCx Example 5 ion plating Comparative Cathode arc
N.A. TiN 3 .mu.m Gold A 0.211 0.82 N.A. 21 N.A. Example 6 ion
plating Comparative Cathode arc N.A. TiAlN 3 .mu.m Reddish A 0.183
1.23 N.A. 24 N.A. Example 7 ion plating brown Comparative N.A. N.A.
N.A. N.A. A N.A. N.A. N.A. N.A. N.A. Example 8 N.A. indicates "not
available" x: written in the column of "Component of Interlayer"
indicate atomic ratio to a metal element
TABLE II Reduction Raman Spectrum ratio in Presence of Presence
Intensity indices Wave number thrust resistance corroded of peaks I
= intensity where peak compared with workpiece Wear or below S =
integral intensity around 1560 cm.sup.-1 Comparative material on
peeling 1,000 cm.sup.-1 I700/I1340 S700/S1340 I1340/I1560
S1340/S1560 appeared Example 8 cutting edge of film Sample 1 Yes
0.03 0.02 1.2 2.7 1560 41 No No Sample 2 Yes 0.04 0.03 1 2.4 1561
43 No No Sample 3 Yes 0.06 0.05 0.7 2.2 1562 42 No No Sample 4 Yes
0.08 0.07 0.8 2.2 1563 45 No No Sample 5 Yes 0.11 0.08 0.3 0.3 1565
47 No No Sample 6 Yes 0.35 0.19 0.1 0.4 1571 51 No No Sample 7 Yes
0.27 0.12 0.2 0.5 1569 48 No No Sample 8 Yes 0.24 0.17 0.4 0.6 1575
54 No No Sample 9 Yes 0.35 0.13 0.3 0.3 1574 56 No No Sample 10 Yes
0.36 0.11 0.4 0.5 1572 61 No No Sample 11 Yes 0.41 0.65 0.2 0.4
1576 65 No No Sample 12 Yes 0.77 0.87 0.3 0.6 1578 67 No No Sample
13 Yes 1.3 1.3 0.2 0.5 1580 69 No No Sample 14 Yes 2.3 2.2 0.2 0.3
1576 45 No No Sample 15 Yes 2.1 1.9 0.2 0.4 1573 42 No No Sample 16
Yes 1.1 0.9 0.1 0.3 1576 41 No No Sample 17 Yes 0.03 0.02 1 2.8
1562 46 No No Sample 18 Yes 0.13 0.08 1.1 2.3 1561 48 No No Sample
19 Yes 0.21 0.17 0.9 2.4 1566 51 No No Sample 20 Yes 0.26 0.25 0.5
2.1 1565 46 No No Sample 21 Yes 0.35 0.18 0.1 0.3 1568 50 No No
Comparative No 0 0 2.2 4.3 1558 99 Accumulation Worn Example 1
confirmed present Comparative Yes 0.23 0.14 0.9 0.5 1571 97
Accumulation Worn Example 2 confirmed present Comparative Yes 0.25
0.13 0.4 0.6 1572 102 Accumulation No Example 3 confirmed present
Comparative Yes 0.21 0.11 0.5 0.8 1575 103 Accumulation Peeling
Example 4 confirmed present Comparative No 0 0 1.9 3.6 1556 95
Accumulation Worn Example 5 confirmed present Comparative No N.A.
N.A. N.A. N.A. N.A. 136 Chipping No Example 6 observed Comparative
No N.A. N.A. N.A. N.A. N.A. 147 Chipping No Example 7 observed
Comparative N.A. N.A. N.A. N.A. N.A. N.A. 100 Chipping N.A. Example
8 observed N.A. indicates "not available"
TABLE III Workpiece material machined A5052 Cutting speed 100
m/min. Feed rate 0.5 mm/rev Cutting depth 40 mm Number of holes
1000 holes (A5052: Japanese Industrial Standards H4000)
According to the results shown in Table II, the TiN film
(Comparative Example 6) and the TiAlN film (Comparative Example 7)
both conventionally used; and the amorphous carbon films of
Comparative Examples 1 to 5 deviating from the specified standard
range had the same level of thrust resistance as did Comparative
Example 8 without a coating. Comparative Examples 1 to 7 were
inferior to Comparative Example 8 in terms of protecting the
cutting edge from the accumulation of the corroded workpiece
material. In contrast, it is apparent that the drills produced
according to the present invention (Samples 1 to 21) demonstrated
excellent wear resistance to the drilling of aluminum and caused
less aluminum to corrode and accumulate on the cutting edges. This
also reaffirms that said drills achieved high precision in the
drilling processing and may last longer.
EXAMPLE 2
In the same method employed in Example 1, an amorphous carbon film
of sample 4 was formed on the substrate of a cemented carbide
reamer with a 4 mm diameter, wherein the diamond sintered body of
Type A was brazed on the cemented carbide reamer as a substrate.
Said diamond sintered body was placed in a closed container
together with a nitric-hydrofluoric acid comprising a 30 mol %
nitric acid and a 45 mol % hydrofluoric acid respectively at the
ratio of 4 to 1. Then, the sintered body was maintained for 12
hours at the temperature of 130.degree. C. to elute components
other than diamond. Thereafter, the sintered body was brazed to
said cemented carbide reamer. For comparison, the same type of
cemented carbide reamers were prepared and are indicated in
Comparative Examples 1 to 8. Comparative Example 1 was coated by a
hydrogenated amorphous carbon film produced through the CVD method.
Comparative Examples 2 to 4 were covered with amorphous carbon
films having a thickness out of the present invention. Comparative
Example 5 was coated by a hydrogenated amorphous carbon film
manufactured through the cathode arc ion plating method, wherein
CH4 was added to the atmosphere gas. Comparative Examples 6 and 7
were covered respectively by a TiN film and a TiAlN film.
Comparative Example 8 had no coating thereon.
Secondly, drilling tests were conducted by the use of aluminum die
cast (ADC12) under the conditions provided in Table IV concerning
said reamers coated with the films respectively produced by the
aforementioned methods. Thereafter, the hole counts and the state
of the cutting edges were examined.
TABLE IV Workpiece material machined ADC12 Cutting speed 230 m/min.
Feed rate 0.15 mm/rev Cutting depth 15 mm (ADC12: the Japanese
Industrial Standards H5302)
As a result of the tests, Comparative Examples 1 to 7 found varied
hole diameters when the hole counts reached 600. Examination of the
reamers revealed that the cutting edges were worn and partly
chipped on the tips. As for Comparative Example 8 having no
coating, it was found that chipping occurred to the cutting edge
soon after the drilling test began when the count reached 3.
On the other hand, the reamer coated with the amorphous carbon film
produced according to the present invention (Sample 4) did not
experience any problems in machining the workpiece material when
the hole count reached 9500. No sign of wear or chipping was
observed.
EXAMPLE 3
In the same method employed in Example 1, an amorphous carbon film
(Sample 6) was formed on the surface of an insert for the endmill
processing, wherein a sintered body (Type E) was brazed to a
substrate of the cemented carbide insert. The insert was
manufactured in a shape specified as TPGN160304 according to the
ISO. For comparison, the same type of inserts were made available
and covered respectively by a hydrogenated amorphous carbon film
produced through the CVD method (Comparative Example 1); amorphous
carbon films having a thickness out of the standard range herein
provided (Comparative Examples 2 to 4); a hydrogenated amorphous
carbon film formed through cathode arc ion plating wherein CH.sub.4
gas was added to the atmosphere (Comparative Example 5); a TiN film
(Comparative Example 6); and a TiAlN film (Comparative Example
7).
Next, endmills coated with said films produced in the
aforementioned manner were tested in the endmill processing of
aluminum die cast (ADC12) under the conditions specified in Table
V. The cutting length and the state of the tool edges were
evaluated individually until the surface roughness of the machined
workpiece material began to deviate from the standard herein
provided.
TABLE V Workpiece material machined ADC12 Cutting speed 300 m/min.
Feed rate 0.1 mm/rev Cutting depth Ad = Rd = 5 mm Ad: axial depth
of the cuts Rd: radial depth of the cuts
The following are the test results (cutting length) of the endmills
coated by the use of the conventional art. Comparative Example 1
having the hydrogenated amorphous carbon film produced through
chemical vapor deposition recorded 25 meters of cutting length
while Comparative Examples 2 to 4 having the amorphous carbon films
whose thickness was out of the standard range herein specified
recorded 80 meters of cutting length. Comparative Example 5 having
the hydrogenated amorphous carbon film deposited through cathode
arc ion plating with CH.sub.4 gas added to the atmosphere achieved
a cutting length of 35 meters Comparative Examples 6 and 7 with
PVD-produced metal nitride films thereon cut respectively 9 meters
of cutting length and 5 meters of cutting length until they began
deviating from the specified standard of the surface roughness at
which point a judgment was made that their lifetime ended.
Thereafter, the tools of Comparative Example 6 and 7 were examined
after the removal of aluminum adhered to the tip thereof. The
deposited films were no longer present and the substrates of cBN
sintered bodies underneath were exposed.
On the other hand, the endmill of Sample 6 maintained the surface
roughness of the machined material within the specified standard
range when the cutting length reached 800 meters. The tool may be
considered to last longer.
EXAMPLE 4
In the same method employed in Example 1, an amorphous carbon film
(Sample 2) was deposited on the substrate of a cemented carbide
insert, wherein a diamond sintered body was brazed to make an
indexable insert as the substrate. In Example 4, the sintered body
of Type A was employed as a substrate. For comparison, the cemented
carbide inserts of the same type were coated respectively with a
hydrogenated amorphous carbon film formed through chemical vapor
deposition (Comparative Example 1), a TiN film (Comparative Example
6), and a TiAlN film (Comparative Example 7). Next, each of the
coated indexable inserts produced in the aforementioned manner was
incorporated in a holder with a diameter of 32 mm and used for the
endmill processing of aluminum die cast (A390) under the conditions
provided in Table VI. Then, the cutting length and the state of the
cutting edges were evaluated until the surface roughness of the
machined material began to deviate from the standard herein
provided.
TABLE VI Workpiece material machined A390 Cutting speed 200 m/min.
Feed rate 0.1 mm/rev Cutting depth Ad = Rd = 3 mm A390:
Al-16.about.18% wt % Si Ad: axial depth of the cuts Rd: radial
depth of the cuts
The results of the aforementioned tests are as follows. The
hydrogenated amorphous carbon film produced through chemical vapor
deposition (Comparative Example 1) recorded a cutting length of 10
meters of cutting length. The PVD-produced metal nitride films
(Comparative Examples 6 and 7) cut respectively 3 meters of cutting
length and 4 meters of cutting length until the surface roughness
of the machined material began to deviate from the standard herein
specified. At this point a judgment was made that the lifetime of
the tools ended. After the removal of aluminum from the coated
drills, the surface of the cutting edges of the drills was
examined. The films were confirmed to be no longer present and the
substrates beneath were exposed.
The endmill of Sample 2 began to deviate from the standard
specified in respect of the surface roughness of the material
machined, when the cutting length reached 700 meters. At this
point, a judgment was made that the lifetime of the tool ended.
While example embodiments have been herein disclosed, it should be
understood that they are not intended to limit the disclosure, but
rather to cover all modifications and present alternate methods
falling within the spirit and the scope of the invention as defined
in the appended claims and their equivalents.
Aside from the foregoing examples, the present invention is
applicable to an indexable insert used for example in other types
of turning tools (represented by drills, endmills, and reamers),
milling cutters, and in other types of cutting tools (including
cutters, knives, and slitters).
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